Since 1966 this cross-national project has had medical- psychiatrists, social scientists and other team members from the psychological and statistical sciences based in New York and London. Studies are concerned with differences between the United States and the United Kingdom in diagnostic practice, in the frequency and type of psychiatric, medical and social disorders, and in patterns of health care. An important part of this work is the development of reliable and valid methods of classifying patients in both countries and the interchange between the two countries of videotaped interviews. Between 1966-1970 the studies included only patients in public mental hopsitals from the age range 20-59 years. During 1971-1792 the team focused on geriatric patients with special reference to the distinction between, and the prognosis of, the organic and the affective disorders. Research activities for 1973-1976 have extended the geriatric work into a community survey of aged persons and their families and a cross-national comparison of the prevalence of psychiatric, medical and social disorders, their treatment and outcome. Additional proposed research for 1975 will involve a feasibility study of a cross-national comparison of the institutional elderly: including the cost and effectiveness of their long term care.